Activity-based excavation modelling in total Lagrangian SPH with pressure-dependent plasticity

We present an activity-based excavation model for underground mining simulations implemented within the total Lagrangian Smoothed Particle Hydrodynamics (TLSPH) framework of SoliDualSPHysics. The model introduces three key features: (1) a smooth cosine-based activity transition that gradually reduces the stiffness, mass, and gravitational loading of excavated particles; (2) a Drucker-Prager plasticity model with closed-form return mapping for pressure-dependent geomaterial behaviour; and (3) a stress diffusion stabilisation term that damps dynamic oscillations in the explicit time integration. The model is validated against the FEM code TOCHNOG using J2 and Drucker-Prager plasticity. For J2, the maximum equivalent plastic strain agrees within 10%. For Drucker-Prager, qualitative agreement is observed with quantitative overprediction attributed to the lower yield threshold at low confining pressure and the inherent dynamic overshoot of explicit time integration.